The present invention relates generally to medical devices, systems and methods. More specifically, the invention relates to devices, systems and methods for passive patient monitoring.
Monitoring patients is an important aspect of patient care in many different settings. In a general care floor or ward of a hospital, for example, monitoring vital physiological signs such as respiratory rate, heart rate and blood pressure is a basic component of patient care. Monitoring the presence or absence of a patient in a hospital bed or in a chair in the patient's hospital room and monitoring patient movement on that bed or chair may also be beneficial in a general care ward or other area of a hospital. If certain patients leave their beds, they run a risk of falling and injuring themselves. If a patient stops moving in bed, it may mean that the patient is dying, is in a coma or is suffering from a medical complication that makes movement difficult or impossible and requires attention. Excessive movement may indicate a seizure or other condition.
Patients in general care areas of hospitals are typically monitored only intermittently, due to practical difficulties such as lack of staff and resources. Vital signs of a patient on a general care floor, for example, are typically taken every 3-4 hours by a nurse or medical technician. At the same time, as the population ages and hospital admissions are postponed by HMOs and other managed care providers, the severity of hospital patient health problems increases and the number of patients overall increases. Thus, hospital populations continue to increase and hospital patients typically require closer monitoring than they did in the past. A significant and expanding nursing shortage, however, makes increased direct patient monitoring through increased staffing impractical, if not impossible.
Physiological monitoring is equally important in other settings. For example, when a patient undergoes a surgical procedure under conscious sedation, such as in an outpatient operating suite in a hospital or surgi-center, or in a procedure room of a physician's private clinic, the patient's respiratory and heart rates should be continuously monitored. Standards set by the Joint Committee for Accreditation of Healthcare Organizations (JCAHO) require such continuous monitoring of respiratory and heart rates, to detect and prevent adverse effects of sedating medications on patients undergoing procedures under conscious sedation. Other contexts in which physiological monitoring may be important include infant monitoring to detect early signs of sudden infant death syndrome (SIDS), operating room patient monitoring, monitoring of patients during emergency transport, nursing home and skilled nursing facility patient monitoring, home monitoring and the like.
Failing to adequately monitor patients may have grave consequences in any of a number of settings. In a hospital, elderly patients who should remain in bed often become disoriented, leave their beds, and sustain injuries such as fractured hips, arms or wrists. Statistics show that over 25% of elderly hip fracture patients may never leave the hospital after receiving treatment for such a fracture. Another patient may die quietly in a hospital room during a 4-hour period between monitoring checks by a nurse. The patient's family may be highly upset to learn that the death might have been prevented or at least postponed long enough for them to be present. In other examples, vital physiological functions such as lung or heart function may deteriorate significantly without detection, due to insufficient monitoring. Thus, the opportunities for adverse medical events and medical malpractice liability are pervasive on a general care ward of a hospital and in other settings where continuous, accurate patient monitoring is impractical or impossible using currently available systems.
Current systems for patient monitoring do not generally provide for convenient, constant, around-the-clock monitoring. On a general care ward of a hospital, for example, monitoring typically consists of a team of nurses circulating from patient to patient, at three- or four-hour intervals, to take vital signs such as respiratory rate and heart rate. In some hospitals, this monitoring may be augmented by one or more devices, such as a bedside pulse-oximeter, which monitors pulse and oxygen saturation via a small clamp-like device attached to a patient's finger. The pulse-oximeter may be designed to sound an alarm, if a certain pulse or oxygen threshold level is reached. One example of such a system is the Oxinet® II Central Station Network, available from Nellcor (www.nellcor.com). Pulse-oximeters do not measure respiratory rate, however, which is often one of the earliest signs of patient distress. The method for measuring respiratory rate that is most typically used in a general care hospital setting is direct observation by a nurse, certified nursing assistant or the like, which is highly inaccurate, due to the difficulty of counting respirations from merely watching a patient's chest movement. Other currently available methods for measuring respiratory rate include impedance pneumography, which is complex and rarely used outside of the neonatal intensive care unit setting, and capnography, which is also difficult and requires at least that the patient be attached to a nasal canula. Other currently available monitoring systems attempt to measure other patient parameters. These include electrocardiography (ECG) transmitters, used in a telemetry unit to monitor heart physiology in patients. ECG electrodes are attached directly to a patient's skin and a transmitter coupled with the electrodes is carried by the patient so that physiological data related to the patient's heart function can be transmitted to a central monitoring station. Blood pressure cuffs may be attached to patients and programmed to intermittently, automatically take blood pressure readings.
These currently available systems and methods for patient monitoring have several characteristics in common. Virtually all require a patient to be physically connected to a monitoring apparatus. Many, such as automatic blood pressure cuffs, provide only for intermittent monitoring. Physical connection to monitoring apparatus can be cumbersome and inconvenient for patients, sometimes leading to patient noncompliance, such as when a patient removes a device due to discomfort. Attached devices may also loosen, change position, fall partially off the patient and the like, leading to inaccurate monitoring data. Intermittent monitoring can lead to missed or late diagnosis and adverse patient outcomes, especially in very sick patients whose conditions may change rapidly.
Current systems also do not monitor patient movement or positioning, such as on a patient bed or chair. As described above, patient movement can be an essential monitoring tool. For example, complete absence of patient movement on a bed could indicate that the patient has left the bed. Relatively slight movement, a significant reduction in movement or the like could indicate that the patient is sufficiently still that some medical problem might have occurred. Significant increases in patient movement might indicate a seizure or significant patient discomfort.
Therefore, it would be advantageous to have devices, systems and methods for passively monitoring one or more patients. Such passive monitoring would ideally be continuous, but would not require inconvenient or cumbersome direct attachment of a device to a patient. It would be advantageous if such passive monitoring could detect motion and/or positioning of a patient on a surface, such as a patient bed or chair, and if respiratory rate, heart rate, and/or other physiological parameters could also be monitored. Ideally, monitoring would include activating an alarm when one or more thresholds were met or when a predefined negative trend occurred, and may also involve providing data to a user in other forms, such as for display on a monitor. It would also be desirable to provide devices and methods for monitoring multiple patients simultaneously. At least some of these objectives will be met by the present invention.